i guess if you think about it, an eeg machine is a low noise high gain
direct coupling subwoofer pre-amp.
On Fri, Mar 12, 2010 at 10:51 AM, Kelly <hurtstotouchfire at gmail.com> wrote:
> Josh or Andreas can send you some data. I'm interested to hear about
> magnetic field noise. I've printed out that paper, so if it doesn't
> cover it, I'll do some googling.
>> I don't think we have DC offset data. Andreas might. We get mostly
> 60 hz in terms of external noise, but there is broad spectrum noise
> when you have bad contact. Getting good contact at the scalp is the
> biggest issue with passive electrodes. I really want to try making
> some active electrodes, to see how much that helps. But I know from
> my experience at Berkeley that even with active electrodes you need
> good contact to keep a good signal.
>> Right now my hope is that we could make a simple 2-4 channel active
> electrode set for forehead electrodes, which will have the best
> contact. Then we can see how much we can get out of that in
> post-processing.
>> -Kelly
>> On Thu, Mar 11, 2010 at 19:30, Albert Alexander
> <albert.alexander at gmail.com> wrote:
>> Hi all,
>>>> I found a great article on noise and circuit design for EEG. Definitely
>> worth reading in entirety:
>>http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2817545/pdf/CIN2010-630649.pdf>>>> Also, that Amphenol connector (24-28s) is standard and available, but is $45
>> a pop. May be wiser to cannibalize that connector that heads to the needles.
>>>> Regarding noise/EMI:
>>>> At low frequencies, magnetic fields are a much bigger issue than electric
>> fields. Magnetic fields are tremendously difficult to shield, especially
>> when one end of the shield is open (the electrode cap). I think shielding
>> for the electrode leads is probably not going to be very helpful. Unless we
>> put the electrode cap inside a metal helmet, which might be pretty sweet.
>>>> We should DEFINITELY twist the plus with the return wire for each of the
>> leads. This should reduce 60 Hz AC noise substantially. It'll help with
>> fluorescent light switching noise, but that stuff is just plain hard to deal
>> with.
>>>> What type of noise have you guys seen on previous readings? Is it mostly
>> high frequency? Is there much DC offset for your input signals? If you have
>> data available I'd love to see it.
>>>> Best regards,
>> Albert
>>>>>>>> _______________________________________________
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>>EEG at lists.noisebridge.net>>https://www.noisebridge.net/mailman/listinfo/eeg>>>>>>>> --
> Kelly Buchanan
> Barker 210E, 510-643-9744
> Helen Wills Neuroscience Institute
> University of California at Berkeley
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